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C7010gl al Teckwilm Page 3 <br /> Dual Phase Extraction Pilot Test Report <br /> Project No 723 2 <br /> November 12,2004 <br /> 2.0 MONITORING WELLS <br /> SJC/EHD approved the installation of three groundwater observation wells in order to <br /> monitor the ISCO process Wells GP-1, GP-2 and GP-3 were placed approximately 13, 22 <br /> and 45 inches, respectively, from the injection well MW-9 These short distances were <br /> necessary to determine the radius of influence of injected chemicals in well MW-9 through <br /> the predominantly clayey soils at the site <br /> ' 2.1 Observation Well Installation <br /> Prior to commencing work, a soil boring/observation well permit was secured and the <br /> SJC/EHD was notified at least 48 hours in advance The subsurface was cleared of <br />' underground utilities by notifying Underground Service Alert <br /> On February 5, 2004, V & W Drilling of Isleton, California mobilized to the site to install <br />' monitoring wells GP-1, GP-2 and GP-3 The borings were drilled to a depth of 19 5 feet <br /> below grade surface (bgs) using a six-inch outside diameter continuous flight hollow stem <br /> auger In each borehole the augers were left in place and then a GeoprobeTM ng was used to <br /> advance the boreholes to a depth of 30 feet bgs The borings were not logged during drilling <br /> due to their proximity to existing on site wells <br />' The wells were constructed with pre-fabricated GeoprobeTM wells The wells are 3/a" <br /> schedule 80 PVC with two (2), flush thread, five--foot screened sections The screened <br /> sections are surrounded with a factory packed 20/40 mesh sand A #3 sand was used to <br /> extend the filter pack above the pre-fabricated sections by 0 5 — 1 feet The following table <br /> includes the wells' construction details <br /> Well No. Diam./TD Screen Slot Sand Pack Transition Grout Seal <br /> (in/ft) Interval (ft) (in) (ft) Seal (ft) (ft) <br /> GP-1 3/4'/28' 18—28' 0 010 17 —28' 14 - 17' 14'-surface <br />' GP-2 3/4"129 5' 19 5 —29 5' 0 010 19 — 30' 16 - 19' 16'-surface <br /> GP-3 3/4"/30' 20- 30' 0 010 19 — 30' 16 - 19' 16'-surface <br /> A transition seal of bentonite chips was installed above the sand(#3) filter pack, hydrated and <br /> allowed to set for thirty minutes The surface seal was achieved by pouring a neat cement <br />' grout (augmented with <5% bentonite) into the borehole while the auger flights were <br /> removed The wells were secured with flush mounted traffic rated well boxes <br />' The well construction details are shown on the boring logs included in Appendix B <br />